R

RIAA Curve: An equalization curve established by the RIAA and applied to all music as it is transferred from master tape to master disc. This pre-emphasis curve introduces a 20dB skew in the frequency content of the program, decreasing the bass content and increasing treble over a 500Hz threshold. The complementary de-emphasis is applied by the phonograph preamplifier during reproduction. Since groove width increases in proportion to the low-frequency content of the program, and since vinyl disc surface noise is most noticeable in the high frequencies, the RIAA curve is designed to enable more dense program recording while minimizing the effect of surface noise.

RIAJ: Record Industry Association of Japan. The Japanese equivalent of the RIAA.

ribbon microphone: A type of dynamic microphone which has a thin metal foil, or ribbon, suspended in a magnetic field. Sound waves vibrate the ribbon in the field and generate an electrical signal. Ribbon mics are usually quite fragile, but are used for their warm, smooth tone quality. They work well with digital recording and on brass instruments to mellow the tone. Ribbon mics are either figure-eight or cardioid. See also condenser microphone.

ribbon tweeter: A high-frequency loudspeaker. The audio signal is connected to the ribbon, which is a very thin (usually aluminum) strip suspended in a magnetic field. The current in the ribbon establishes another magnetic field, causing the ribbon to move in synchrony with the input signal waveform, hence, is a direct radiator of sound. Ribbon tweeters are effective at very high frequencies, and usually require a step-down transformer because of the very low impedance of the ribbon.

riff: A short, catchy musical phrase usually played between lyric lines in a song, often repetitively, thereby acting as a hook.

RIFF: Resource Interchange File Format. A file specification adopted jointly by Microsoft and IBM for multimedia sound applications.

rifle microphone: See gun microphone.

ringing: Any device, electronic or mechanical, is said to ring if it continues to produce a signal or to move after its input is stopped. Ringing, a type of transient distortion, is caused by too little damping, and is particularly prevalent in audio transducers. Low-frequency ringing is called hangover.

ring modulator: A special type of timbre modifier module that accepts two signals as audio inputs and produces their sum and difference tones at its output, but does not pass on the frequencies found in the original signals themselves. This greatly increases the number of harmonics contained in the two sounds and introduces a gross nonlinearity, causing huge amounts of harmonic and intermodulation distortion. The ring modulator is used in the generation of electronic music, usually in conjunction with a lowpass filter which reduces the highfrequency roughness of the resulting metallic sound. It gets its name from its circuit configuration which is a circle, or ring, of four diodes. See also oscillator sync.

ripping: The process of extracting samples from MOD files for use in digital compositions.

ripple: (1) Irregularities in the frequency response of a filter which has a nominally flat response in its passband, or (2) irregularity in the value of DC voltage in a power supply which manifests itself as hum in the loudspeakers.

R

RMS: Root Mean Square. A formula for describing the level of a signal. RMS is derived by squaring all of the instantaneous voltages along a waveform, averaging the squared values, and taking the square root of that number. For sine-like signals,

average power = RMS(voltage) × RMS(current)

The voltage of an audio signal is usually measured in terms of the RMS value of the signal. The RMS value of an alternating current produces the same heating effect in a circuit as the same value of a direct current.

Robinson-Dadson curves: See equal loudness curves.

rock and roll: A system used in dubbing or mixing by which the projector, dubbers, and recorder can run in synchronization in reverse. Thus, if a mistake is made in mixing a particular section, all sources can be rolled back past the mistake, and a new take can be punched-in before the mistake. Also called rollback. Selsyn motors on all machines involved are required to make rock and roll possible.

rollback: (1) See rock and roll. (2) On video recording/editing systems, the rollback, or RLB, function is used to rewind machines by a predetermined amount from the current position. The default rollback time is 15 seconds.

rolloff: (1) The difference between the input amplitude and the output amplitude in a filter over a specified frequency band, expressed in dB. (2) See rolloff filter, rolloff slope.

rolloff filter: A filter which has a reduced output as the frequency is increased is called a rolloff filter. A tone control is a rolloff filter when turned down. Sometimes the attenuated portion of the frequency content of the signal itself is called rolloff. A circuit that attenuates a signal that is above (lowpass) or below (highpass) at specified frequencies. For example, microphones usually have a bass rolloff filter to remove wind noise and/or excessive breath pops.

rolloff frequency: The frequency above or below which a filter begins to filter out the harmonics of the waveform. As the rolloff frequency is raised or lowered, more of the harmonics of the sound will be filtered out. Specifically, the frequency at which the response of an equalizer or other audio device is reduced by 3dB, and can refer to both lowpass and highpass response curves. The rolloff frequencies of an amplifier are the frequencies where the output voltage drops to 0.707 of the middle range output. A decrease of the voltage by a factor of 0.707 is equivalent to -3dB, so these critical frequencies are often referred to as the 3dB down points. Also called cutoff frequency, critical frequency, or the half-power point. Moving the rolloff frequency in real-time will produce a wow effect, which can be accentuated by increasing the filter resonance level.

rolloff slope: The acuity of a filter’s rolloff frequency. Rolloff is generally measured in dB/octave. A shallow slope, such as 6dB per octave, allows some frequency components beyond the rolloff frequency to be heard, but at a reduced volume. When the rolloff slope is steep (on the order of 24dB/octave), frequency components very close to the rolloff frequency are reduced in volume so much that they fall below the threshold of audibility. Rolloff slopes are sometimes called skirts. See filter, pole, sharp(2).

R

room equalization: The alteration of the frequency response of signals that will be sent to speakers or monitors, done in order to compensate for room modes. These problems are generally identified by sending pink noise to the speakers, then adjusting the frequency response of the resulting sound that arrives at the listening position. Most room EQ references use 13 - octave 31-band graphic equalizer, with additional over-all bass and treble adjustments. See also RTA. Also called voicing.

room mode: Also called standing waves, room modes come in three types: axial, along the axes of a room (front to back, side to side, floor to ceiling); tangential, or any two pairs of opposite surfaces; and, oblique modes which are the product of the reflections of all six surfaces. To calculate the frequency of a particular mode,

f	c		nx		2	ny	2	nz		2
	2		Lx			Ly		Lz

Where f is in Hertz, c is the speed of sound (1130 ft./sec. or 344 meters/sec.), L is the room dimension, and n is the order of the mode. It’s not important to know the frequencies of the room mode, just how evenly spaced they are. If they are not uniformly distributed, the room will show a response peak where they are nearly coincident. The most problematic frequency range is 50Hz-150Hz. The golden ratios of height to width to length are: 1.14:1.39:1 or 1.28:1.54:1 or 1.60:2.33:1 (Bolt’s golden ratios), then the modes will be perfectly spaced and low-frequency response is smooth by design. See also standing wave.

room sound: The characteristic ambient sound of a concert hall or other listening space.

room tone: The ambient noise of a room, set or location where dialog is recorded for the production shoot. Usually recorded as wild sound, room tone is used by film and dialog editors as a bed to form a continuous tone through a particular scene. Not to be confused with ambience, which can be sound effects and/or reverberation added when the dialog is mixed. See also NC Curve, walla.

root: The lowest note of an uninverted chord, and therefore the note which usually gives the chord its name. For example, in a triad, it is the lowest note when the chord is arranged as two thirds on top of one another: C is the root of the chord of C (C, E, and G), an arrangement known as root position. If the root is not the lowest note, the triad is said to be inverted.

root mean square: See RMS.

rotary head: The video recording system that uses a rotating drum carrying two or more heads which sweep across the tape at a small angle, typically 5˚-8˚. This allows a high rate of scanning to be combined with a low tape speed.

R

rotation point: In a compressor or expander, the input signal level at which the graph of the device’s transfer characteristic intersects its unity gain curve. At this level, there is no net change from input to output level.

	Level	2:1 Compression Ratio
	Output
		Rotation Point
		4:1 Compression Ratio
	0dB	Input Level

Rotation Point

rough cut: A stage in the editing of the workprint or videotape at which the scenes and shots are in order and cut approximately to their correct length, between an assembly and a fine cut. See copy editing.

rough mix: A mix of a recording in progress, either as it occurs or, in the particular case of a stereo mixdown of a multitrack recording, one made at the end of a day’s work for overnight audition.

routing: (1) (verb) The process of directing a signal from one point to another. (2) (noun) The pathway a signal takes, e.g., through which busses it passes on a mixing desk.

Rt: See stereo optical print.

RT-60: The reverberation time of a space. Suggested times for various room volumes are:

Room Vol. (103 cu.ft.)	Range of RT-60 Times (seconds)
1-2	0.3-0.4
2-3	0.3-0.55
3-5	0.4-0.65
5-7	0.45-0.7
7-10	0.5-0.75
10-15	0.55-0.8
15-20	0.65-0.9

R

RT-60 meter: A hardware device for measuring the acoustical characteristics of a listening/recording space. Gated pink noise is played and analyzed by the meter. The meter then provides a read-out of the locations reverb profiles for the different frequencies, usually 125Hz, 250Hz, 500Hz, 1kHz, 2kHz, and 4kHz.

RTA: Real-Time Analyzer. A piece of hardware that measures the loudness of an audio signal, either through a flat-response microphone or a line input, and categorizes the loudness into different frequency bands, used to flatten out the frequency response of a monitoring system. An RTA usually displays frequencies at one third-octave or octave bands. The decibel level of each frequency band is displayed graphically.

RTSP: Reat-Time Streaming Protocol. An internet protocol for real-time transmission of highfidelity audio, suitable for live concert feeds as well as professional audio applications. See

RealAudio.

rubato: A musical term indicating that a conductor or musician may take expressive liberties with the tempo during the designated section of a score.

rumble: A low-frequency mechanical vibration in a turntable, microphone, or tape transport. Rumble is specified as a S/N ratio in decibels, with -50dB being common.

rumble track: Stereo white noise lowpass filtered at about 40Hz so as to be felt and not heard.

run: A command used by DOS to launch an application program. The RUN command may be used with various switches (subcommands) and is uniquely powerful and straightforward. This is no doubt owing to the sacred–cow status of the command conferred by its origin in the numerous progenitors of DOS, decades before anyone from Microsoft could confuse it.

running master: The same as a print master.

running status: A data compression scheme for MIDI data whereby status bytes can be skipped if they would be the same as the most recent status byte. For example, a four-note chord can be transmitted using only nine bytes rather than the usual twelve. See also MIDI delay(2).

rushes: See dailies.

rustle: See Foley.

S

S: Side. The difference component of a stereo signal, i.e., the components which come from the side of the stereo field. See M & S.

S & S: Sampling and Synthesis. A term used to describe synthesizers which combine elements of these processes to produce their sound.

Sabine equation: The reverberation time of a room is found using the Sabine equation:

RT60 = 0.049 × (V/Sa)

where V is the volume of the room in cubic feet, Sa is the total number of sabins present, and RT-60 is the reverberation time.

sabin: The efficiency with which materials in a room absorb sound and damp reverberation is measured in sabins, abbreviated Sa. The number of sabins of absorption is found by multiplying the number of square feet of a particular material by the absorption coefficient of that material. Also spelled sabine.

SACD: Super Audio Compact Disc. Philips/Sony’s proposal for a next-generation CD which combines DVD technology to produce a hybrid disc that will play in conventional CD players, but offering better audio quality than currently available CDs when played in a DVD player.

The upper later is the “conventional (Red Book) layer, while the lower layer provides around 4.7 Gb of high-density storage, increasing the audio capacity to 4.7Gb, the same as a firstgeneration DVD, and allow text, graphics, and video alongside audio. Audio will be encoded via either standard 16-bit PCM at 44.1kHz, or “Super Audio” using Sony’s DSD data format and Philips’ DST data compression technologies, yielding 74 minutes of six-channel audio with purportedly a frequency response of DC–1MHz and the same dynamic range as conventional digital recordings of 24–bit/96kHz resolution. SACD employsSBM noise-shaping, and PSP copy protection. The intention of the SACD standard is to ultimately combine a stereo DSD track and a six-channel DSD surround mix, plus optional data, text, graphics, and video data.

Here is a comparison between conventional (Red Book) CD and (the current (3/99) prototype specification for) SACD:

	Conventional	Super Audio
	Compact Disc	Compact Disc
Diameter	4-3/4” (120mm)	4-3/4” (120mm)
Thickness	1/20” (1.2mm)	1/20” (1.2 mm)
Signal Sides	One	One
Signal Layers	One	Two
Data Capacity
Reflective Layer	780 Mb	780 Mb
Semi-Transmissive Layer		4.7 Gb
Audio Coding”
Standard Audio	16-bit PCM, 44.1 kHz	16-bit PCM, 44.1 kHz
Super Audio		1-bit DSD, 2.8224 MHz
Multichannel	2-channel	6 channels of DSD
Frequency Response	5-20,000 Hz	DC-1MHz
Dynamic Range	< 96 dB	< 120 dB
Playback Time	74 minutes	74 minutes
Enhancements	CD Text	Text, Graphics, Video